This invention relates to the art of making bags equipped with reclosable extruded plastic zippers.
As heretofore constructed, extruded zipper equipped bags have generally been provided with separate zipper strips having complementary profiles which are separably enterengagable. This has required producing and handling two separate zipper strips in the bag making process where the strips are separably formed and attached to the bag body sheet or web material. On the other hand, where the profiles are integrally extruded with the film, it has been required to extrude separate complementary profile portions of the zipper on separate panels or panel portions of a bag making film.
In a recent development as covered in the copending application of Christoff and Ausnit, Ser. No. 574,878, filed Jan. 30, 1984 now U.S. Pat. No. 4,617,683, and assigned to the same assignee as the present application, it has been proposed to provide zippers formed from extruded profiled continuous strips folded upon themselves so that the profiles on the folded strip portions interlock to provide reclosable zippers for the bags. In that application it has also been proposed to notch out the zipper profiles at the fold in the strip to facilitate folding of the zipper strip portions upon themselves. However, there has been some problem at the zipper fold in that memory factor of the plastic material tends to spread the fold which may cause a leakage problem at that point. Such leakage may be either of contents from within the bag, or intrusion of foreign matter including air into the bag.